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It's okay to hate Al Gore. (Photo credit: Wikipedia)

We have reached the point where every rational person who believes in making decisions based on science and available data should, if not fully believe that human beings are warming the planet by releasing greenhouse gases, at least recognize that this is what the data seem to suggest and that it is what the vast majority of scientists who study weather believe is the case.

Recognizing this does not force anyone to oppose pipelines, support a carbon tax, or start composting and wearing hemp shoes. It just opens us up to start aiming our fiery furnace of a political system at actually solving our problems. Go ahead, argue that the economic cost of anti-greenhouse measures doesn't justify the benefit, especially if the planet is getting too hot. Argue that we should look for technical solutions not only to reduce carbon dioxide and methane emissions but not to suck the stuff out of the atmosphere – although then you might find yourself standing with Bill Gates and calling for more investment in R&D. If you want to wade into the science, argue that the worst-case scenarios are overstatements.

Below follow some of the main objections that have come up over the past year or so when I discussed this issue with conservative friends who do not believe in global warming – and the reasons why I think those objections have been covered.

But warming stopped.

No it didn't. The global temperature is rising, but it also bounces around a lot. Between 1998 and 2005, average global temperature did not increase. But that's because 1998 was really hot. An abnormally strong El Nino caused heat to move from the ocean into the atmosphere. Besides being cherry-picking, this also ignores warming in the ocean, scientists say.

The Earth is getting warmer, but it's too much of a leap to say that human beings are the reason. There are plenty of natural climate cycles and I believe in being skeptical.

Fair enough. But this is science, and skepticism has to come within the framework of what we already understand. The scientific method does not simply mean coming up with an idea, or hypothesis, and testing it to see if it is true.

Hypotheses are supposed to be based on our existing body of understanding – based on our current theory. These get tested before wilder and crazier ideas. We don't just leap to testing whether aliens are using the planet as a dump for the heat from their warp drives.

It's certainly true that climate can change dramatically over time, and has. There have been ice ages and hot periods. But right now, there are not obvious candidates for other explanations of current warming. For instance, the sun seems to be cooling.

“There's no way of explaining what's happened in the last 50 years through natural cycles,” says Donald Wuebbles, the Harry E. Preble Professor of Atmospheric Science at the University of Illinois.“We have no evidence of a natural cycle that can do anything like this. It also exactly fits with all our knowledge of what happens with carbon dioxide and greenhouse gases. We've known about greenhouse gases since 1824! We know the oceans are warming, the atmosphere's warming, the land is warming. It's all happening in tune with each other.”

Wuebbles says “there's no basis for trying to make up something because you'd like that to be true” and that “you can't dream up natural cycles as if that will work.”

A natural cycle still seems more likely than the idea that we've made the atmosphere into a giant heat tent.

The main reason for believing that the atmosphere is a giant heat tent is that this has been the basis of climate science for nearly 200 years. Joseph Fournier, the great mathematician, first made calculations about how the atmosphere keeps the Earth warm in 1824. John Tyndall, a physicist, established that particular gasses, including water vapor but also methane and carbon dioxide, resulted in heat being trapped in the atmosphere. The Swedish scientist, Svante Arrhenius, showed in 1896 that more carbon dioxide would mean warming and predicted that industrial output could eventually warm the planet. The greenhouse effect is the main explanation for why Venus is super-hot – the hottest planet in the solar system – and Mars is super-cold. So this isn't an out-there idea. It's an outgrowth of our basic theory, our understanding, of how the warming of planets works, and it has been tested again and again. These are not new ideas, and they are not based entirely on computer models.

Scientists are just trying to get government money.

Dangling grant money is a great way to shift the priorities and perspectives of scientists, but it doesn't tend to lead them to make things up. Most of the scientists who are arguing for global warming could probably make more money if they went to work for industry. Also, controversial ideas get published all the time, and there would be a Nobel Prize in proving that warming isn't happening.

Everything Al Gore says is wrong.

In our interview and during a press conference at the annual meeting of the American Association for the Advancement of Science in Boston this weekend, Wuebbles actually agreed that misstatements by Gore had led to a backlash.

“Most of what is pretty good but there's a few comments that are over-exaggerations,” says Wuebbles. “That's typical Al. I've known him for years. He gets it, he understands it, but he has the ability to overstate it and some of those overstatements are where he gets in trouble.”